iPedia Free Information Center

Information about Sebum

Schematic view of a hair follicle with sebaceous gland.
Cross-section of all skin layers.A hair follicle with associated structures. (Sebaceous gland labeled at center left.)
Latinglandula sebacea
subject #234 1069
MeSH Sebaceous+glands
Dorlands/Elsevier g_06/12392642
The sebaceous glands are glands found in the skin of mammals.

Locations and morphology

A branched type of acinar gland, these glands exist in humans throughout the skin except in the palms of the hands and soles of the feet.

Sebaceous glands can usually be found in hair-covered areas, where they are connected to hair follicles. The glands deposit sebum on the hairs, and bring it to the skin surface along the hair shaft. The structure consisting of hair, hair follicle, and sebaceous gland is known as a pilosebaceous unit.

Sebaceous glands are also found in non-haired areas of eyelids, penis, labia minora, and nipples. Here, the sebum traverses ducts which terminate in sweat pores on the surface of the skin.

At the rim of the eyelids, meibomian glands are a specialized form of sebaceous gland. They secrete sebum into the tears coating the eye, to prevent evaporation.

Sebum

Sebaceous glands secrete an oily substance called sebum (Latin, meaning fat or tallow) that is made of fat (lipids) and the debris of dead fat-producing cells. In the glands, sebum is produced within specialized cells and is released as these cells burst; sebaceous glands are thus classified as holocrine glands.

Sebum is odorless, but its bacterial breakdown can produce odors. Sebum is the cause of some people experiencing "oily" hair if it is not washed for several days. Earwax is partly composed of sebum.

Function

Sebum acts to protect and waterproof hair and skin, and keep them from becoming dry, brittle and cracked. It can also inhibit the growth of microorganisms on skin.

Composition

The composition of sebum varies from species to species; in humans, the lipid content is as follows:[1]

Percent compositionSubstance
25%wax monoesters
41%triglycerides
16%free fatty acids
12%squalene

Changes during development

The sebaceous glands of a human fetus in utero secrete a substance called Vernix caseosa, a "waxy" or "cheesy" white substance coating the skin of newborns.

The activity of the sebaceous glands increases during puberty because of heightened levels of androgens. In males, sebaceous glands begin to appear predominantly on the penis during and after puberty. This is however normal, not to be confused with an STD. In females, they appear predominantly in the labia minora.

Pathology

Sebaceous glands are involved in skin problems such as acne and keratosis pilaris. The prescription drug isotretinoin significantly reduces the amount of sebum produced by the sebaceous glands, and is used to treat acne.

The extreme use (up to 10 times doctor prescribed amounts) of anabolic steroids by bodybuilders for muscle gain and repartitioning effects tend to stimulate the sebaceous glands which can cause acne.[2]

A blocked sebaceous gland can result in a sebaceous cyst.

A condition involving enlarged sebaceous glands is known as sebaceous hyperplasia.

Sebaceous gland carcinoma is a rare and aggressive form of cancer involving the sebaceous glands; sebaceous adenoma is a more benign neoplasm of the sebaceous glands.

Importance to other animals

Certain species of Demodex mites feed on sebum and are commonly found in the sebaceous glands of mammals, including those of humans.

The preputial glands of mice and rats are large modified sebaceous glands that produce pheromones.

Additional images


Sagittal section through the upper eyelid.

A hair follicle with associated structures.


References

1. ^ Jeffrey B. Cheng and David W. Russell. Mammalian Wax Biosynthesis II: Expression Cloning of Wax Synthase cDNAs Encoding a Member of the Acyltransferase Enzyme Family, J Biol Chem. 2004 Sep 3;279(36):37798-37807. PMID 15220349 Fulltext
2. ^ Abuse Of Anabolic Steroids Causes Acne In Bodybuilders, by Medinda.com

External links

 •  • [ e]
Integumentary system
structuresSkin • Sweat glands • Sebaceous glands • Hair (Hair follicle) • Nails • Scale
layersEpidermis (Stratum corneum, Stratum lucidum, Stratum granulosum, Stratum spinosum, Stratum germinativum/basale) • Dermis • Subcutis
Latin}}} 
Official status
Official language of: Vatican City
Used for official purposes, but not spoken in everyday speech
Regulated by: Opus Fundatum Latinitas
Roman Catholic Church
Language codes
ISO 639-1: la
ISO 639-2: lat
..... Click the link for more information.
Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. Created and updated by the United States National Library of Medicine (NLM), it is used by the MEDLINE/PubMed
..... Click the link for more information.
Elsevier, the world's largest publisher of medical and scientific literature, forms part of the Reed Elsevier group. Based in Amsterdam, the company has substantial operations in the UK, USA and elsewhere.
..... Click the link for more information.
gland is an organ in an animal's body that synthesizes a substance for release such as hormones, often into the bloodstream (endocrine gland) or into cavities inside the body or its outer surface (exocrine gland).
..... Click the link for more information.
Skin layers: epidermis, dermis, and subcutis, showing a hair follicle, sweat gland & sebaceous gland.]] In zootomy and dermatology, skin is the largest organ of the integumentary system made up of multiple layers of epithelial tissues that guard underlying muscles and organs.
..... Click the link for more information.
Mammalia
Linnaeus, 1758

Subclasses & Infraclasses
  • Subclass †Allotheria*
  • Subclass Prototheria
  • Subclass Theria

..... Click the link for more information.
alveolar glands[1] (or saccular glands[2][3], or acinar glands[4], or acinous glands[5][6]).
..... Click the link for more information.
Palm or Palms may refer to:
  • The central region of the front of the hand
  • Arecaceae or palm tree, a family of flowering plants belonging to the monocot order Arecales
  • Sago palm or Cycas revoluta

..... Click the link for more information.
The sole is the bottom of the human foot. Anatomically, the sole of the foot is referred to as the plantar aspect. The equivalent surface in ungulates is the hoof.

Description


..... Click the link for more information.
A hair follicle is part of the skin that grows hair by packing old cells together. Attached to the follicle is a sebaceous gland, a tiny sebum-producing gland found everywhere except on the palms, lips and soles of the feet.
..... Click the link for more information.
An eyelid is a thin fold of skin and muscle that covers and protects an eye. With the exception of the prepuce and the labia minora, it has the thinnest skin of the whole body. The levator palpebrae superioris muscle retracts the eyelid to "open" the eye.
..... Click the link for more information.
For the symbol of the erect penis, see phallus.
The penis (plural penises, penes) is an external sexual organ of certain biologically male organisms.
..... Click the link for more information.
The labia minora (singular: labium minus) are two small longitudinal cutaneous folds, situated between the labia majora, and extending from the clitoris obliquely downward, lateralward, and backward for about 4 cm.
..... Click the link for more information.
nipple is an appurtenance from which a fluid emanates, in this instance breast milk, to nurture a mother's young.

Anatomy

In the anatomy of mammals, a nipple or mammary papilla
..... Click the link for more information.
The meibomian glands (or tarsal glands) are a special kind of sebaceous glands at the rim of the eyelids, responsible for the supply of sebum, an oily substance that prevents evaporation of the eye's tear film, prevents tear spillage onto the cheek, and makes the closed
..... Click the link for more information.
Tears are a liquid produced by the body's process of lacrimation to clean and lubricate the eyes. The word lacrimation may also be used in a medical or literary sense to refer to crying. Strong emotions, such as sorrow or elation, may lead to crying.
..... Click the link for more information.
Eyes are organs of vision that detect light. Different kinds of light-sensitive organs are found in a variety of organisms. The simplest eyes do nothing but detect whether the surroundings are light or dark, while more complex eyes can distinguish shapes and colors.
..... Click the link for more information.
Latin}}} 
Official status
Official language of: Vatican City
Used for official purposes, but not spoken in everyday speech
Regulated by: Opus Fundatum Latinitas
Roman Catholic Church
Language codes
ISO 639-1: la
ISO 639-2: lat
..... Click the link for more information.

Fat

Fat may refer to:
  • Fat, a group of compounds that are generally soluble in organic solvents and largely insoluble in water
  • Adipose tissue, an anatomical term for loose connective tissue composed of adipocytes

..... Click the link for more information.
Tallow is also a component of the WiX installer software.
Tallow is rendered mutton, beef or other bovine fat, processed from suet. (Rendered fat obtained from pigs is known as lard.)

The tallow derived from beef is called stearin.
..... Click the link for more information.
Lipids can be broadly defined as any fat-soluble (hydrophobic), naturally-occurring molecules. The term is more-specifically used to refer to fatty-acids and their derivatives (including tri-, di-, and monoglycerides and phospholipids) as well as other fat-soluble sterol-containing
..... Click the link for more information.
Editing of this page by unregistered or newly registered users is currently disabled due to vandalism.
If you are prevented from editing this page, and you wish to make a change, please discuss changes on the talk page, request unprotection, log in, or .
..... Click the link for more information.
Holocrine is a classification of exocrine glands in the study of Histology.

Holocrine secretions are produced within the cell followed by the rupture of the plasma membrane, thus releasing the cellular contents into the lumen.
..... Click the link for more information.
Bacteria

Phyla

Actinobacteria
Aquificae
Chlamydiae
Bacteroidetes/Chlorobi
Chloroflexi
Chrysiogenetes
Cyanobacteria
Deferribacteres
Deinococcus-Thermus
Dictyoglomi
Fibrobacteres/Acidobacteria
Firmicutes
Fusobacteria
..... Click the link for more information.
Earwax, also known by the medical term cerumen, is a yellowish, waxy substance secreted in the ear canal of humans and many other mammals. It plays an important role in the human ear canal, assisting in cleaning and lubrication, and also provides some protection from
..... Click the link for more information.
Hair is a filamentous outgrowth of protein, found only on mammals. It projects from the epidermis, though it grows from hair follicles deep in the dermis. Although many other organisms, especially insects, show filamentous outgrowths, these are not considered "hair".
..... Click the link for more information.
Esters are a class of chemical compounds and functional groups. Esters consist of an inorganic or organic acid in which at least one -OH (hydroxy) group is replaced by an -O-alkyl (alkoxy) group.
..... Click the link for more information.
Triglyceride   (help info ) (more properly known as triacylglycerol   (help info ) or triacylglyceride
..... Click the link for more information.
Types of Fats in Food
  • Unsaturated fat
  • Monounsaturated fat
  • Polyunsaturated fat
  • Trans fat
  • Omega: 3, 6, 9

..... Click the link for more information.
Squalene is a natural organic compound originally obtained for commercial purposes primarily from shark liver oil, though there are botanic sources as well, including amaranth seed, rice bran, wheat germ, and olives. All higher organisms produce squalene, including humans.
..... Click the link for more information.


This article is copied from an article on Wikipedia.org - the free encyclopedia created and edited by online user community. The text was not checked or edited by anyone on our staff. Although the vast majority of the wikipedia encyclopedia articles provide accurate and timely information please do not assume the accuracy of any particular article. This article is distributed under the terms of GNU Free Documentation License.
Herod_Archelaus


page counter